Cellulose fluff pulp is a common component in the core of disposable absorbent products, such as diapers, catamenials, and incontinent pads. Cellulose fluff pulp is relatively inexpensive. Superabsorbent polymer (SAP) in fiber or powder form is another component that is often found in the core of disposable absorbent products. Core materials like cellulose fluff pulp, chemically modified fluff pulp, or SAP are not easily desorbed because the thermodynamic attraction of aqueous liquids for these materials is extremely high. Hence, liquid in a region containing these materials generally cannot be transported through or away from that region making fluid distribution difficult. Cellulose fluff pulp also collapses when saturated with liquid. This collapse has long been a problem in the absorbent products art limiting their utility.
U.S. Pat. No. 4,898,642 to Moore et al.; U.S. Pat. No. 4,888,093 to Dean et al.; U.S. Pat. No. 4,889,596 to Schoggen et al. and U.S. Pat. No. 4,976,819 to Minton describe various chemically modified fluff pulps directed to remedy the deficiencies of untreated fluff pulp.
U.S. Pat. No. 3,219,739 to Breen discloses poly(ethylene terephthalate) (PET) fibers and a process for making those fibers. The fibers disclosed in the '739 patent are characterized by having arms, a relatively high spatial frequency, and relatively short-range sinuous (ruffle) or spiral geometries in the arms. The relatively short range is on the order of ten microns. The fibers disclosed in the '739 patent will not spontaneously transport water. That is, a liquid in contact with the cross-section of a single one of the fibers disclosed in the '739 patent will not continuously spread from the place of contact along the length of the fiber.
U.S. Pat. No. 5,611,981 to Phillips et al. discloses spontaneously wettable fibers having a combination of X values and surface contact angles that satisfy conditions for spontaneous wetting. The X factor is defined therein as X=P.sub.w /(4r+(.pi.-2)D) where P.sub.w is the wetted perimeter of the filament, r is the radius of the circumscribed circle circumscribing the fiber's cross-section, and D is the minor axis dimension across the fiber's cross-section. The teachings of the '981 patent are hereby incorporated herein by reference as if fully set forth herein.
U.S. Pat. No. 5,200,248 to Thompson et al. discloses capillary channel polymeric fibers, which store and transport liquid. The fibers have non-round cross-section shapes which include relatively long thin portions. The cross-section shapes are the same along the length of the fiber. The '248 patent discloses that these capillary channel fibers may be coated with materials that provide an adhesion tension with water of at least 25 dynes/cm. The teachings and especially the definitions in the '248 patent are hereby incorporated by reference as if fully set forth herein.
U.S. Pat. No. 5,268,229 to Phillips et al. discloses fibers having non-round cross-sectional shapes, specifically "U" and "E" shaped cross-sections with stabilizing legs. These fibers are also spontaneously wettable fibers and have cross-sections that are the same along the length of the fiber.
U.S. patent application Ser. No. 08/912,608, filed Aug. 15, 1997, now U.S. Pat. No. 6,103,376, issued Aug. 15, 2000, discloses bundles of fibers for use as distribution materials. The individual fibers themselves are poor distribution materials having no intra-fiber capillary channels. When combined with each other in bundles, the bundles become excellent distribution materials by utilizing inter-fiber capillary channels. The teachings of and especially the definitions are hereby incorporated herein by reference as if fully set forth herein.